Advanced Bash-Scripting Guide

Chapter 6. Exit and Exit Status...there are dark corners in the Bourne shell, andpeople use all of them.--Chet RameyThe exit command may be used to terminate a script, just as in a C program. It can also return a value, whichis available to the script's parent process.Every command returns an exit status (sometimes referred to as a return status or exit code). A successfulcommand returns a 0, while an unsuccessful one returns a non-zero value that usually may be interpreted as anerror code. Well-behaved UNIX commands, programs, and utilities return a 0 exit code upon successfulcompletion, though there are some exceptions.Likewise, functions within a script and the script itself return an exit status. The last command executed in thefunction or script determines the exit status. Within a script, an exit nnn command may be used to deliveran nnn exit status to the shell (nnn must be a decimal number in the 0 - 255 range).When a script ends with an exit that has no parameter, the exit status of the script is the exit status of thelast command executed in the script (previous to the exit).#!/bin/bashCOMMAND_1. . .# Will exit with status of last command.COMMAND_LASTexitThe equivalent of a bare exit is exit $? or even just omitting the exit.#!/bin/bashCOMMAND_1. . .# Will exit with status of last command.COMMAND_LASTexit $?#!/bin/bashCOMMAND1. . .# Will exit with status of last command.COMMAND_LASTChapter 6. Exit and Exit Status 44